Drawing appliance



May 15, 1951 A. G. WILLIAMS ETAL DRAWING APPLIANCE 2 Sheets-Sheet 1 Filed Dec. 18, 1945 J a w 12 ffmw 5 6W. M .2 Jim A Z 2% B .May 15, 1951 A. G. WILLIAMS ETAL 2,553,026

DRAWING APPLIANCE v Filed Dec. 18, 1945 2Sheets-Sheet 2 an M. Moore Patented May 15, 1951 DRAWING APPLIANCE Arthur George Williams, Ashton, and Donovan Mark Moore, Bristol, England, assignors to Isometric Projections Limited, London, England, a British company Application December 18, 1945, Serial No. 635,753 In Great Britain October 13, 1944 Section 1, Public Law 690, August 8, 1946 Patent expires October 13, 1964 3 Claims.

This invention relates to drawing appliances and has for its object to provide an improved appliance for making parallel perspective drawings from a plan or normal view.

According to the present invention a drawing appliance comprises a tracing point, a drawing point, a linear reducing linkage constraining the drawing point to follow the movements in one direction only of the tracing point to a proportionally reduced extent, and means constraining the drawing point to follow the movements of the tracing point in the direction normal to the first direction.

According to a feature of the invention, the reducing linkage is adjustable to vary the reduction ratio it provides. Preferably the aforesaid means is constituted by a second linear reduction linkage which is adjustable to vary the reduction ratio it provides, so that the original drawing can be copied'both in perspective and to a reduced scale.

According to another feature of the invention, the drawing appliance comprises two tracing slides arranged at right angles to and crossing one another and each constrained by levers to move parallel to itself, a tracing carriage carried by both of the tracing slides to slide along them and carrying the tracing point, two copying slides arranged one parallel to each tracing slide and crossing one another and each constrained by levers to move parallel to itself, means for adjusting the effective length of each lever constraining the copying slides, a copying carriage mounted on both copying slides to slide along them and carrying the drawing point, a link connecting one lever supporting one tracing slide to one lever supporting the parallel copying slide to provide one reduction linkage; and a second link connecting one lever supporting the other tracing slide to one lever supporting the other copying slide to provide the other reduction linkage.

A drawing appliance in accordance with this invention will now be described, by way of example only, with reference to the accompanying drawings in which the two figures show respectively the two halves of a plan view of the appliance which is divided along the chain dotted line,

Figure 1 being the left hand half and showing the tracing mechanism whilst,

Figure 2 is the right hand half and shows the copying mechanism.

The appliance comprises a drawing board I (Figure 1) on which the original drawing is mounted. A radius arm I l is pivoted at one end 2 l2 on a supporting arm l3 which is articulated at Hi and pivoted on a fixed support l5 so that it can be swung clear of the drawing board [0 or adjusted to bring the pivot I2 over the centre of a circle on the original drawing wherever that centre may be on the board III. A slide [6 can he slid along the radius arm II and locked in any position therealong. This slide is articulated to a tracing carriage ii, the articulation being so arranged that the slide and carriage can readily be separated and the carriage carries a tracing point on the axis of the articulation between the slide and the carriage; the radius arm facilitates the tracing of circles of various radii by the tracing point.

The carriage is mounted on a tracing slide bar is by four rollers l9 and also on a tracing slide bar 20, by four similar rollers 2|. The bar [8 is supported to move parallel to itself by two levers 22 which are pivoted at 23 on a fixed bracket 24. The levers 22 are interconnected by a link 28 and one is connected to a link 29.

The bar 20 is supported to move parallel to itself by two levers 25 which are pivoted at 26 on a fixed bracket 21. The levers 25 are connected to a link 30.

It will be seen that movement of the tracing carriage I? to move the tracing point parallel to the tracing bar 20 moves the tracing bar I8 parallel to itself and thus moves the link 29 to a proportional extent. Similarly movement of the tracing carriage parallel to the bar It moves the link 30 to a proportional extent. Any movement of the tracing point over the board ID will thus be translated into a proportional movement of the link 29 and/or the link 30.

The mechanism described above is duplicated, with certain modifications, as shown in Figure 2, and the parts shown in this figure have been given the same reference as the corresponding parts shown in Figure 1 but with the suffix C. It will be seen that the link 29 is connected to one of two levers 22C that support a copying slide bar I for parallel motion while the link 30 is connected to levers 250 that support another copying slide bar 200 for parallel motion. The bars [80 and 29C support a drawing carriage I'IC which carries a pencil or other drawing point 3| over a drawing board IGC. It will be seen that the drawing point 3| will follow the movements of the tracing point exactly if the levers 22 and 220 were of the same effective length and the levers 25 and 250 were also of the same effective length and the appliance would then make an exact copy of the original drawing. The effective lengths of the levers 22C and 25C can be varied in the following way.

A slide 32 is mounted to slide along each lever 22C and can be clamped in any desired position therealong. Each slide 32 is pivoted to the slide bar 180. Thus, by adjusting the slides 32, the.

' efiective length of each lever 226 can be made less in that direction. A linear reduction, of, 0.72 is thus provided. Similar provision is made for. adjusting the effective length of the levers 25C- and is shown for a linear reduction of unity.

It will be understood that the: apparatus will, with the adjustment shown, reproduce the original drawing to the same scale but in perspective, the horizontal dimensions being reduced while the vertical dimensions are unaltered. The mechanism can be adjusted to reduce the vertical dimensions proportionally while keeping the horizontal dimensions unaltered or to reduce the dimensions in different proportions in both directions, depending on the nature of the perspective drawing being made. It will be obvious that the perspective drawing can be made to a smaller scale if required.

The. drawing board I is mounted to slide in its own plane on rails 33, so that it can be moved to space successive parts of a drawing properly. Thus in making the drawing shown, the rectangle portion of the original is traced with the board shifted to. the right from the position shown, the whole drawing on the board is traced in the position of the board lilC shown, and the right-hand part of the circle is traced with the board LOG shifted to the left to obtain the half, ellipse to the right. The tracings are then joined by horizontal lines as shown by dotted lines. this board can be. adjusted. The drawings may be turned on the drawing boards to allow of, say, the front, one side and the top of an article being drawn in perspective from the, original and fitted properly together.

The claim:

1. A drawing appliance comprising, a tracing point, a tracing board over which the tracing point is movable, a drawing point, a drawing board over which the drawing point is movable, a linkage transmitting the movements in one direction only of the tracing point, a second linkage transmitting the, movements in a direction normal to the first direction of. the tracing point, proportionate control means receiving the movements transmitted by at least one of said linkages and proportionately changing the extent of these movements, means constraining the drawing point to follow the movements transmitted by the two linkages and the proportionate control means, and means for shifting the drawing board relative the tracing board in the direction of the smaller scale of reproduction.

A scale may be provided to. which 2. A drawing appliance comprising a tracing board, a tracing point movable over the tracing board, a drawing board, a drawing point movable over the drawing board, two tracing slide bars arranged at right angles to and crossing one another, levers constraining each tracing slidebar to move parallel to itself, a tracing carriage carried by both of the tracing slide bars to slide" along them and carrying the tracing point, two copying slide-bars; arranged one parallel to each tracing slide-bar and crossing one another, levers constraining each copying slide-bar to move parallel to itself, means for adjusting the effective length of each lever constraining the copying slide-bars, a copying carriage mounted on both copying slide-bars to slide along them and carrying the drawing point, a link connecting one lever supporting the tracing slide-bar to one lever supporting the parallel copying slide-bar to provide one reduction linkage, a second link connecting one lever supporting the other tracing, slide-bar to one lever supporting the other copying slidebar to provide the other reduction linkage, and means for shifting. the drawing, board relative to the tracing; board in a direction parallel to one of the slide-bars.

3. A drawing appliance comprising a tracing board, a supporting member, aradius arm pivoted to the supporting 'member, which supporting member is adjustable to; vary' the position of the pivot over the extent of the tracing board, a tracing point, connected to the radius arm at a point adjustable along the length of the radius arm, a drawing point, a drawingboardover which the drawing point is movable, a linkage transmitting the movements in one direction only of the tracing point, a second linkage transmitting the movements in a direction normal to the first direction of the tracing point, proportionate control means receiving the movements transmitted by at least one of said linkages and proportionately changing the extent of those movements, means constraining the drawing point to follow the movements transmitted by the two linkages and the proportionate control means, and means for shifting the drawing board relative. the tracing board in the direction of the smaller scale of reproduction.

ARTHUR WILLIAMS. DONOVAN MARK MOORE.

REFERENCES CITED The following references are of record in. the file of this patent:

UNITED STATES PATENTS Number Name. I Date 260,463 Earle July 4, 1882 637,263, Jacobs Nov. 21, 1899 1,443,088 Pasquariello Jan. 23, 1923 1,484,702 Dowling Feb. 26, 1924 2,021,809 Plese Nov. 19, 1935 2,409,290 Lipp Oct. 15, 19.46

FOREIGN PATENTS Number Country v Date 27,646 Germany June 23, 1884 49,917 Germany Dec. 9, 1889 

